1. Field of the Invention
The present invention relates to a dental tray. More particularly, the present invention is concerned with a dental tray designed to be used for preparing the denture bases of plate dentures, precise impression-taking with the use of light-curing materials and curing the light-curing materials filled in teeth cavities.
2. Statement of the Prior Art
In the present disclosure, the term "denture base" refers to a plate portion forming the base of a plate denture and coming into direct contact with the mucosal surface of the cavity. Thus, the denture base is a part of the plate denture serving to stably maintain the plate denture in the oral mouth and transmit the occlusal pressure to the mucosal surface of the oral cavity, and is the core of the finished plate denture. In general, the denture bases of plate dentures are prepared through very numerous steps by an indirect method with heat- or light-curing resins.
The preparation of the denture bases with a heat-curing resin involves the so-called "preparatory steps" for reproducing the intramouth state on a working model, which comprises:
taking a preliminary impression using a ready-made tray and an impression material,
pouring gypsum slurry into the obtained preliminary impression to form a gypsum model,
pressing a self curing resin against the gypsum model to form an individual tray,
taking a precise impression using the individual tray obtained and an impression material, and
pouring gypsum slurry into the obtained precise impression to form a working model. After the preparatory steps, the denture bases are prepared by the steps of:
forming a bite plate on the working model with wax and attaching it to an articulator,
arranging artificial teeth on the bite plate to form a wax denture,
placing the wax denture in a dental flask and investing it in gypsum,
filling a heat-curing resin in the vacant space of the wax denture removed and curing, and
digging up the cured resin, followed by polishing.
Thus, the denture bases and plate dentures are prepared through very numerous steps. As disclosed in Japanese Patent Laid-Open Publication No. 60(1985)-90552, on the other hand, the preparation of denture bases and plate dentures using a light-curing resin involves the so-called "preparatory steps" for reproducing the intramouth state on a working model, which comprise:
taking a preliminary impression using a ready-made tray and an impression material,
pouring gypsum slurry into the obtained preliminary impression to form a gypsum model,
pressing a self curing resin against the gypsum model to form an individual tray,
taking a precise impression using the individual tray obtained and an impression material, and
pouring gypsum slurry into the obtained precise impression to form a working model. After the preparatory steps, the denture bases are prepared by the steps of pressing a light-curing resin against the working model and applying active energy rays to the resin for the polymerization and curing thereof. To finish the plate dentures, formation of alveolar ridges portion, arrangement of artificial teeth and formation of gingival portion are further formed on the obtained denture bases with the use of a light-curing resin.
In the case of the denture bases of plate dentures obtained through such steps, it is impossible to remove errors occurring in the course of the preparatory steps of preparing the denture bases wherein the intramouth state is reproduced on the working model, since they are prepared on the basis of the working model. Nor is their fitting accuracy satisfactory. Further, very numerous steps are still required to prepare the denture bases of plate dentures.
That the steps of preparing the denture bases of plate denture is very numerous and difficulty is encountered in obtaining the denture bases of improved fitting accuracy is considered to be attributable to the fact that the dental tray is designed only for the purpose of taking impressions in the course of the so-called "preparatory steps" wherein the intramouth state is reproduced on the working model, and to the prejudice that the dental tray should not, or cannot, be used for the main steps of the preparation of denture bases.
The prior art dental trays include a ready-made tray for preliminary impression-taking and an individual impression tray for precise impression-taking and individual tooth impression tray for each tooth impression-taking. These trays have been provided for the exclusive purpose of taking impressions in the steps wherein the intramouth state is reproduced on the working model. Thus, the ready-made and individual trays have generally been made of a metallic or hard plastic material and a self curing resin or organic compound, respectively, with a main view to preventing them from transforming easily due to the forces applyed thereto during the pressing step or removal step of impressions. In other words, any substantial attention has not been paid to their active energy rays-transmitting property. Nor has any consideration been taken into account as regards the possibility that they might have been used for the later steps in preparing the denture bases of plate dentures. As the dental trays having active energy rays-transmitting property, Japanese Patent Laid-Open Publication No. 61(1986)-41447 discloses a dental tray comprising a transparent rigid material such as transparent hard plastics or glass. However, the dental tray disclosed in this Japanese Patent Laid-Open Publication No. 61(1986)-41447 is a ready-made tray designed to be exclusively used for impression-taking in the course of the steps of reproducing the intramouth state on the working model, as is the case with the conventional dental tray. For that reason, certain limitation is previously imposed upon the size and shape of such a dental tray by the manufacturer, and is formed of a rigid material difficult to transform, so that it cannot be transform to suit the intramouth contour, and thus be used as an individual tray. Thus, although it is possible to use the dental tray disclosed in Japanese Patent Laid-Open Publication No. 61(1986)-41447 as a ready-made tray for preliminary impression-taking, yet it is difficult to use such a dental tray as the individual tray for precise impression-taking. Still more, it is very difficult to use such a dental tray for the preparation of the denture bases of plate denture.